Not Applicable.
Not Applicable.
(1) Field of the Invention
The present invention relates to a lock assembly for locking an outer tubular element to an inner tubular element extending through the outer tubular element. Such lock assemblies are, for example, applied in a wellbore for the production of hydrocarbon fluid from an earth formation. In such application the outer tubular element can be connected to (or integrally formed with) the wellbore casing or a wellbore production tubing, and the inner tubular element is adapted to receive a wellbore device (e.g. a valve).
(2) Background of the Invention
A problem with such applications comes to light when the lock assembly is subjected to longitudinal forces. For example, when the inner element is subjected to a longitudinal force due to fluid pressure of produced hydrocarbon fluid, such force can lead to relative movement between the two elements leading to loosening of the lock connection. Furthermore, such relative movement prevents adequate transmission of signals, e.g. acoustic or electric signals, between the inner and outer tubular elements. A further problem occurs with applications involving conventional dog and lock shoulders whereby the inner tubular element is subjected to radially inward forces upon application of a pulling force, thus requiring an increased wall thickness of the inner tubular element.
Accordingly it is an object of the invention to provide an improved lock assembly which overcomes the problems of the conventional lock assemblies.
In accordance with the invention there is provided a lock assembly for locking an outer tubular element to an inner tubular element extending through the outer tubular element, the assembly comprising a lock mandrel connected to one of said tubular elements and being provided with a recess facing the other one of said tubular elements, the recess having at least one inwardly diverging side surface, a lock member arranged between the first and second tubular elements in a locking relationship with the other one of the tubular elements, the lock member extending into said recess and being operable between a retracted mode in which the lock member is movable relative to the recess and an expanded mode in which the lock member is expanded against the inwardly diverging side surface, the assembly further comprising an actuator means for expanding the lock member in said recess against said diverging side surface.
It is thereby achieved that when the lock member is in the expanded mode, a load applied to the lock assembly, e.g. a longitudinal pulling force, induces the lock member to become even more firmly locked in the recess due to the inwardly diverging side surface of the recess. Thereby the locking action of the assembly is enhanced. Furthermore, it is thereby ensured that the inner and outer elements are in firm contact with each other allowing adequate transmission of electric or acoustic signals.